Differential pressure switch



Oct. 17, 1961 R. E. LEIBOLD ET AL 3,005,067

DIFFERENTIAL PRESSURE SWITCH Filed March 50, 1959 2 Sheets-Sheet 1 INVENTORS RICHARD E. LEIBOLD YA TON 0.090 AIR Jr.

QWATTORNEYS Oct. 17, 1961 R. E. LElBOLD ETAL DIFFERENTIAL PRESSURE swrrcn 2 Sheets-Sheet 2 Filed March 30. 1959 INVENTORS RICHARD ameom BY ALTON G. De LA] E Jr. 'Wf fl tp '2 ATTORNEYS United States Patent The present invention relates to a differential pressure switch, and more particularly to a switch operable in accordance with the differential between two pressures and adapted to open and close .at different pressure differentials.

It is an object of the present invention to provide a switch of the character described having switch contacts located in a switch chamber filled with electrically insulating oil.

It is a further object of the present invention to provide a pressure diflerential switch comprising a housing having two separated diaphragms therein defining a pair of separated pressure chambers and an intermediate switch chamber, said switch chamber having a stationary switch contact therein, a movable switch contact carried by one of said diaphragms, said switch chamber being filled with an electrically insulating oil, and means for connecting said pressure chambers to two different sources of pressure.

More specifically,'it is an object of the present invention to provide a switch of the character described including pressure responsive means for effecting relative movement between a pair of switch contacts and magnetic hysteresis means effective to provide opening and closing movement 1 of said contacts to occur at different pressure differentials.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawing, illustrating a preferred embodiment of the invention, wherein:

FIGURE 1 is an elevational view of the switch.

FIGURE 2 is a plan view sectioned on the line 2-2, FIGURE 3.

FIGURE 3 is a side elevational view with parts broken away.

FIGURE 4 is a fragmentary view of the contact su porting spider.

FIGURE 5 is an exploded view of the components of the differential switch.

The pressure differential switch disclosed herein comprises fluid pressure responsive means operable upon attainment of a predetermined pressure differential between two pressure sources to effect opening movement of the contacts of a switch and operable in response to attainment of a predeterminedly different pressure differential for effecting closing of the switch. In' general terms this is accomplished by providing magnetic hysteresis means including a magnet and a magnetic member moved into engagement with the magnet upon a predetermined switch actuation so that a substantially different pressure differential is required to eflect a reverse switch actuation.

In the embodiment of the invention illustrated herein, the magnetic hysteresis means is operable upon opening between the magnet and the magnetic member must be overcome to initiate closing movement of the switch contacts.

Referring now to the drawings the differential switch comprises a support body 10 having a generally circular portion shaped to provide annular inwardly facing grooves 12 forming diaphragm seats at opposite sides thereof surrounding a central opening 14. Extending into the central opening are a plurality of circumferentially sepmovement of the switch contacts so that the attraction arated arms 15 which together form a spider for support- ICC? . 2 ing a stationary switch contact 16 mounted in an insulating disc 18. g

In the groove 12 at one side of the support body is flexible diaphragm 20, the peripheral portion of which is clamped and sealingly engaged in the groove by a backing ring 22. At the opposite side of the body 10 the flexible diaphragm 24 has its peripheral portion received in the groove 12 and sealingly engaged therein by the backing ring 26. I

Carried by the flexible diaphragm 24 is an electrical switch contact 28 which as best seen in FIGURE 5 includes an integral or separate disc or armature portion 30 formed of magnetic material. The diaphragms 20 and 24 cooperate with the generally central portion of the support body 10 to define between the diaphragms a switch chamber 32. A closure plate 34 is provided on the body 10 and has openings therethrough as indicated at 36 for receiving the electrical conductors 38 and 40 which are sealed in the openings and which are connected respectively to the switch contacts 16 and 28.

The interior of the switch chamber 32 is completely filled with an electrically insulating oil. This oil serves two useful functions in the present switch. In the first place it completely surrounds the switch contacts 16 and 28 and effectively prevents arcing when the switch is operated. Secondly, since the switch chamber is completely filled with the oil, it serves as a means for mechanically connecting the diaphragms 20 and 24.

At one side of the support body 10 is a hollow cap 42 which cooperates with the diaphragm 20 to form a first'pressure chamber 44. The cap 42 has a threaded opening 46 which receives an adjustable spring support 48 at the inner end of which is provided a spring seat 50. Intermediate the spring seat 50 and a spring pilot 52 on the diaphragm '20 is a compression spring 54 which urges the diaphragm 20 to the right.

At the opposite side of the support body 10 is' a similarly formed hollow cap 56 defining with the support body and the flexible diaphragm 24 a second pressure chamber 58. Mounted on an insulating ring 60 in the cap 56 is a magnet 62 having a peripheral mounting portion 64 which may be formed of insulating material. The magnet is retained in assembled positionby a cup-like retainer 66 having a central opening through which a polar end portion 68 of the magnet extends.

The magnet 62 is annular and has a central opening 70 therethrough. The cap 56 has an opening 72 in which is received a compression spring 74 the upper end of which engages a spring insulator 76 which in turn engages against the lower side of the disc portion 30 of the'contact '28. The lower portion of the opening 72 receives a spring adjusting screw 7-8 the inner end of which carries a spring seat 80 which engages the lower end of the compression spring 74.

Means are provided for connecting the pressure chambers 44 and 58 to different sources of pressure. For example, the pressurechamber 44 has a port 82 adapted to be connected by an external conduit 84 to a source of low pressure. Similarly, the pressure chamber 58 is provided with a port 86 adapted to be connected by an external conduit 88 to a source of relatively high pressure. Thus, the conduits 84 and 88 may for example be connected to a fluid passage at different points having a flow restriction therebetween and thus make the switch responsive to flow through the passage.

With the foregoing construction it will be observed that the adjustable spring 54 acts to move the diaphragm 20 to the right as seen in FIGURE 2, whereas the spring 74 acts to move the diaphragm 24 to the left. Since the interior of the switch chamber 32 is completely filled with incompressible electrically insulating oil, the diaphragms move as a unit. Accordingly, the fluid pressure differential in the chambers 32 and 58 required to open the switch contacts 16 and 28 is determined by the adjustment of the springs 54 and 74. However,1when the, switch opens in response to an appropriate pressure differential, the movable armature portion 30 of the contact 28 moves into contact with the pole face of the magnet 62. Accordingly, initiation of switch closing movement requires that the attraction between the magnet and its armature be broken. l Inasmuch as the attraction between the magnet and the armature, when they are in intimate contact, represents a substantial force and since this ,force drops to a negligible fraction as soon as contact is broken, it will be appreciated that closing movement of the switch takes place at a substantially greater pressure differential than is required to open the switch contacts. Moreover, the abrupt termination of the effectiveness of the magnet in preventing initiation of switch closing movement of the contact 28 results in a pressure differential of sufficient magnitude being built up to cause abrupt and complete closure of the switch contacts. 7

It will further be appreciated that adjustment of the spring 74 is affected primarily in determining the pressure differential required to initiate closing movement .of the switch. 7

Switch vopening and closing of this differential pressure switch occurs at separately adjustable pressure differentials. In other words, the switch may be regarded as comprising means incorporating an adjustable differential tripping or opening point and a separately adjustable hysteresis for the closing point. V The drawing and the foregoing specification constitute a description of the improved differential pressure switch in such full, clear, concise and exact terms as to enable any person skilled in the artlto practice the invention, the scope of which is indicated by the appended claims.

What we claim as our invention is: 1. A differential pressure switch comprising a support body having an opening therethrough, a pair of laterally spaced seats at opposite sides of said opening, diaphragms on said seats defining therebetween and with the portion of said body surrounding the opening a central switch chamber, spider means on said body supporting a switch contact generally centrally of said switch chamber, electrically insulating oil filling said switch-chamber, hollow caps overlying said diaphragms and sealed to said body to.defi ne pressure chambers therewith, means for connecting .the interior of said pressure chambers with different. sources of fluid pressure, an electrical contact carried by one of said diaphragms and movable thereby into and out of contact with said first mentioned contact, resilient means within one pressure chamber operatively engaging the diaphragm forming a part of said one pressure chamber and biasing said diaphragms in switch opening direction, a magnet fixed in said other pressure chamber, a magnetic member on said other diaphragm movable into engagement with a pole of said magnet when said diaphragms are in switch open position. 2. A differential pressure switch comprising a support body having an opening therethrough, a pair of laterally spaced seats at opposite sides of said opening, diaphragms on said seats defining therebetween and with the portion of said body surrounding the opening a central switch chamber, spider means on said body supporting a switch contact generally centrally of said switch chamber, electrically insulating oil filling said switch chamber, hollow caps overlying said diaphragms and sealed to said body to define pressure chambers therewith, means for connecting the interior of said pressure chambers with different sources of fluid pressure, an electrical contact carried by. one of said diaphragms and movable thereby into and out of contact with said first mentioned contact, resilient means within one pressure chamber operatively engaging the diaphragm forming a part of said one pressure chamber and biasing said diaphragms in switch opening direction, a magnet fixed in said other pressure chamber, a magnetic member on said other diaphragm movable into engagementwith a pole of said magnet when said diaphragms are in switch open position, and adjustable resilient means in said other pressure chamber operatively engaging a portion movable with said diaphragms to variably control the pressure differential required to separate said magnet and magnetic member to initiate switch closing movement of said diaphragms.

3. A differential pressure responsive contact switch effective to provide opening and closing movement of the contacts at different pressure differentials comprising a housing having a pair of spaced flexible diaphragms therein dividing the interior of said housing into a pair of separated pressure chambers and an intermediate switch chamber, a high pressure source connected to one of said chambers and a low pressure source connected to the other of said chambers, stationary and movable switch contacts in said switch chamber, said movable contact being carried by the diaphragm forming part of the high pressure chamber, a magnet and an armature positioned in the high pressure chamber, said armature being movable with respect to said diaphragms, an electrically insulating oil filling said switch chamber and effective to provide a force transmitting connection between said dia phragms, said switch being effective to opensaid contacts at a first pre-selected differential pressure between said pressure chambers whereby said armature is attracted to engage said magnet and said switch being effective to close said contacts at a second pre-selected differential pressure which overcomes the magnetic forces tending to hold the armature and magnet togetherl 4. A differential pressure responsive contact switch effective to provide opening and closing movement of the contacts at different pressure differentials comprising a housing having a pair of spaced flexible diaphragms therein dividing the interior of said housing into a pair of separated pressure chambers and intermediate switch chamber, a high pressure source connected to one of said chambers and a low pressure source connected to the other of said chambers, stationary and movable switch contacts in said switch chamber, said movable contact being carried by the diaphragm forming part of the high pressure chamber, a'magnet and an armature positioned in the high pressurechamber, said armature being movable with respect to said diaphragms, an electrically insulating oil filling said switch chamber and effective to provide a force transmitting connection between said diaphragrns, saidswitch being effective to open said contacts at a first pre-selected differential pressure between said pressure chambers whereby said armature is attracted to engage said magnet and said switch being effective to close said contacts at a second pre-selected differential pressure which overcomes the magnetic forces tending to hold the armature and magnet together and resilient means within said low pressure chamber operatively engaging the diaphragm forming a part of said low pressure chamber and biasing said diaphragms in switch opening direction. i

5. A differential pressure responsive contact switch effective to provide opening and closing movement of the contacts at different pressure differentials comprising a housing having a pair of spaced flexible diaphragms therein dividing the interior of said housing into a pair of separated pressure chambers and intermediate switch chamber, a high pressure source connected to one of said chambers and a low pressure source connected to the other of said chambers, stationary and movable switch contacts in said switch chamber, said movable contact being carried by the diaphragm forming part of the high pressure chamber, a magnet and an armature positioned in the high pressure chamber, said armature being movable with respect to said diaphragms, an electrically insulating oil filling said switch chamber and etfective to provide a force transmitting connection between said diaphragms, said switch being effective to open said contacts at a first pre-selected ditierential pressure between said pressure chambers whereby said armature is attracted to engage said magnet and said switch being effective to close said contacts at a second pre-selected differential pressure which overcomes the magnetic forces tending to hold the armature and magnet together, resilient means within said low pressure chamber operatively engaging the diaphragm forming a part of said low pressure chamber and biasing said diaphragmsin switch opening direction and additional resilient means in said high pressure chamber connected to said diaphragms when said armature and magnet are engaged to apply a force to said diaphragms tending to separate said armature and magnet.

6. A differential pressure responsive contact switch effective to provide opening and closing movement of the contacts at different pressure differentials comprising a housing having a pair of spaced flexible diaphragrns therein dividing the interior of said housing into a pair of separated pressure chambers and an intermediate switch chamber, a high pressure source connected to one of said chambers and a low pressure source connected to the other of said chambers, a stationary switch contact in said switch chamber, a movable switch contact and armature unit, said movable contact extending through the dia phragm forming part of the high pressure chamber into said switch chamber, said armature being located in the high pressure chamber and movable with respect to the movement of said diaphragms, a magnet positioned in the high pressure chamber, means retaining the magnet in an assembled position, an electrically insulating oil filling said switch chamber and effective to provide a force transmitting connection between said diaphragms, said switch being effective to open said contacts at a first preselected difierential pressure between said pressure chambers whereby said armature is attracted to engage said magnet and said switch being effective to close said contacts at a second pre-selected difierential pressure, which is larger than said first differential pressure, said second differential pressure overcoming the magnetic forces tend: ing to hold the armature and magnet together.

7. A differential pressure responsive contact switch 9 Y O defined in claim 6 wherein located within the low pressure chamber operatively engaging the diaphragm forming a part of said low pressure chamber and biasing said diaphragms in switch opening direction.

8. A differential pressure responsive contact switch defined in claim 7 wherein additional adjustable spring means are provided in the high pressure chamber connected to said diaphragms whensaid armature and magnet are engaged to apply a force to said'diaphragms tending to separate said armature and magnet.

9. A dilierential pressure switch comprising a support body having an opening therethrough, a pair of laterally spaced seats at opposite sides of said opening, movable walls on said seats defining therebetween and with the portion of said body surrounding the opening a central switch chamber, means on said body supporting a switch contact generally centrally of said switch chamber, electrically insulating oil filling said switch chamber, hollow caps overlying said movable walls to define pressure chambers therewith, means for connecting the interior of said pressure chambers with different sources of fluid pressure, an electrical contact carried by one of said walls and movable thereby into and out of contact with said first mentioned contact, resilient means within one pressure chamber operatively engaging the wall forming a part of said one pressure chamber and biasing said walls in switch opening direction, a. magnet fixed insaid other pressure chamber, a magnetic member on said other walll movable into engagement with a pole of said magnet when said walls are in switch open position.

References Cited in the file of this patent UNITED STATES PATENTS adjustable spring means are 

